The present application is the national stage under 35 U.S.C. 371 of PCT/EP98/00021, filed Jan. 16, 1998.
1. Technical Field of the Invention
The present invention relates to a manually operated aerosol inhalation device comprising a holding part for receiving an aerosol container with a valve and an outlet tip, and an inspiratory part, which at one end comprises a mouthpiece, in which inspiratory part a member for passage of aerosol is provided for receiving the outlet tip of the aerosol container and comprising a conduit with an outlet opening for discharging charging aerosol into the inspiratory part in the direction towards the mouthpiece. Such inhalation devices are for instance known from DK-B-146675, DK-B-164082, DK-B-169464 and DK-B-169863.
2. Prior Art
DK-B-146675 describes an aerosol inhalation device with a swingably openable lid which in its closed position covers an inserted aerosol container to prevent activation thereof and which covers the mouthpiece to prevent it from becoming dirty.
DK-B-164082 describes an aerosol inhalation device with a lid and a rear piece, which are hinged in such a way that the rear piece, when the lid is open, acts as a trigger to facilitate activation of the aerosol container for dispensing a dose of aerosol.
DK-B-169464 describes an aerosol inhalation device, in which the member for passage of aerosol is designed with a special discharge spout which prevents depositing of hygroscopic aerosol particles at the outlet from the member for passage of aerosol.
DK-B-169863 describes another aerosol inhalation device with measures for preventing clogging of hydroscopic aerosol particles at the outlet from the member for passage of aerosol.
Common to these aerosol inhalation devices is, however, that air cannot flow freely through the device past the member for passage of aerosol and out through the mouthpiece, the flow path towards the member for passage of aerosol being partly blocked by the aerosol container. The area of the flow cross section from the surroundings to the member for passage of aerosol to the mouthpiece is thus substantially limited relative to the area of the flow cross section from the member for passage of aerosol to the mouthpiece. This is a problem, as for instance asthmatics, which constitute a big group of users of aerosol inhalation devices, have difficulty in providing sufficient air flow for bringing the active particles of the aerosol down into the lungs. As a matter of fact in case of known devices only approx. ⅓ or less of the active particles is deposited in the lungs, whereas the rest is deposited in the mouth and the throat, where it is undesirable from a medical point of view.
The known manually operated aerosol inhalation devices are used in the manner that the user exhales into free air and then puts the inhalation device to his mouth, inspires and simultaneously presses on the aerosol container, for instance via a trigger, such that a dose of aerosol is dispensed. The air passage next to the container itself is, as mentioned, limited and does not provide the possibility of a proper inhalation through the mouth. The contents of the aerosol are injected as a jet of mist into the mouth towards the rear part of the throat, where the air flow from the nose catches the aerosol and takes its active particles and vehicles down into the lungs. By this method the mouth cavity acts like a relatively dead area with heavy fall-out of particles, and it is only possible for the part of the particles, which remains suspended in the air, to be brought further down into the lungs by means of the air flow from the nasal intake of breath. Through good coordination and technique about one third or less of the active particles is deposited in the lungs by this method, and the rest is deposited at the back of the throat, where it is not desirable from a medical point of view. A comparatively huge intake of breath is required to catch the suspended particles and to take them to the lungs, and in that respect asthmatics are often not able to produce such an intake of breath or account of the asthma. The depositing of the active particles of the aerosol in undesired places may besides have some side effects in the form of local irritations or may for instance result in fungus. Therefore, patients are told to rinse the mouth after use of the aerosol, a request which however, is often not complied with.
In addition to the above manually operated aerosol inhalation devices, breath-activated devices are known, see for instance DK-B-136018, which shows a mechanic device, and WO-A-96/30068, which shows a computer-controlled device. Common to these devices is, however, that they provide a pressure drop, which is used for activating a device for dispensing a dose of the aerosol. These pressure drops, however, undesirable for the above reasons.
U.S. Pat. No. 4,984,158 discloses an apparatus for training a correct breathing performance and coordination with a view to the best possible exploitation of an inhalation device. The apparatus comprises an inspiration member which at one end is provided with a mouthpiece and at its other end is provided with a flow-measuring device which provides a pressure drop, just as in case of the above-mentioned breath activated aerosol inhalation devices. The inspiration member carries a manually operated aerosol container, the discharge tip of which points downwards towards a baffle plate which is to guide the sprayed aerosol towards the mouth of the user. Such a baffle plate is, however, unreliable and thus unsuitable for conducting the aerosol in the desired direction.
Finally, DK-B-151934 discloses a powder inhalation device with a venturi-shaped air passage conduit for spraying a powderous medicament which is taken down into the air passage duct at its narrowest place. There is generally a considerable difference in the considerations forming the basis of the design of an inhalation device for powders, which are allowed to drop down in an inspiratory air flow and the considerations forming the basis of the design of an inhalation device with a pressurized aerosol container, which sprays out the substance.
The object of the invention is to provide an aerosol inhalation device which does not suffer from the above drawbacks of the prior art.
The object is according to the invention met by an aerosol inhalation device of the type mentioned by way of introduction and which is characterized in that at the end opposite the mouthpiece the inspiratory part is open towards the surroundings such that air may pass freely from the surroundings past the member for passage of aerosol and out through the mouthpiece, i.e. that the pressure drop at the flow of air from the surroundings to the member for passage of aerosol is not substantially bigger than the pressure drop occuring by the passage of air through the inspiratory part from the member for passage of aerosol to the mouthpiece.
In a preferred embodiment the area of the flow. cross section in the inspiratory part, possibly apart from the area around the member for passage of aerosol, is substantially constant. This contributes to keeping down the pressure drop through the inspiratory part.
In a further preferred embodiment the member for passage of aerosol is at its exterior side aerodynamically designed such that it offers the least possible resistance to the air flow in the inspiratory part and creates the least possible turbulence.
The outlet end of the conduit in the member for passage of aerosol is designed as a diffusor. In this way such a reduction of the velocity of the sprayed out aerosol is obtained that it is mainly taken in by the user through inspiration rather than sprayed into the mouth of the user.
In a practical embodiment the inspiratory part is a cylindrical tube which is open at both ends and between its ends carries the holding part for the aerosol container.